1. Field of the Invention
The present invention relates to a pattern forming method, a method for producing an electronic device using the same, and an electronic device. More particularly, the present invention relates to a pattern forming method which is suitable for semiconductor production processes for integrated circuits (ICs) and the like, production of circuit boards such as liquid crystals and thermal heads, and lithographic printing processes for photopublication applications, a method for producing an electronic device using the pattern forming method, and an electronic device. In particular, the present invention relates to a pattern forming method which is suitable for the exposure by means of an ArF exposure apparatus that uses far-ultraviolet light having wavelength of 300 nm or less as a light source, an ArF liquid immersion type projection exposure apparatus, and an extreme ultraviolet (EUV) exposure apparatus, a method for producing an electronic device using the pattern forming method, and an electronic device.
2. Description of the Related Art
Along with the miniaturization of semiconductor elements, shortening of the wavelength of exposure light sources and an enhancement of the numerical aperture (high NA) of projection lenses are in progress. Furthermore, a so-called liquid immersion method is known which is intended to increase the resolving power by shortening the wavelength, and involves filling of the space between the projection lens and a sample with a liquid having a high refractive index (hereinafter, also called “immersion liquid”). The liquid immersion method is effective for all types of pattern shapes, and the miniaturization of patterns and an enhancement of resolving power have been achieved by combining the liquid immersion method with super-resolution technologies such as a phase shift method, a modified illumination method, double patterning, and Reflow.
Furthermore, since the development of resists for a KrF excimer laser (248 nm), an image forming method called chemical amplification has been used as a resist image forming method, in order to compensate for a decrease in the sensitivity caused by light absorption. To explain the mechanism by taking an example of the image forming method based on positive type chemical amplification, it is an image forming method in which an acid generator at an exposed area is decomposed by exposure to produce an acid, an alkali-insoluble group is converted to an alkali-soluble group through a process of post exposure bake (PEB) by using the generated acid as a reaction catalyst, and the exposed area is removed by alkali development. The positive type image forming method utilizing this mechanism of chemical amplification is currently considered as mainstream.
However, in recent years, there has been a demand for further advanced miniaturization of patterns. Recently, a technology has been disclosed, in which resist films that are obtained by using not only the positive type chemical amplification resist compositions of the current mainstream but also negative type chemical amplification resist compositions, are developed using organic developers (see, for example, JP4554665B).
In the positive type image forming method, isolated line or dot patterns can be satisfactorily formed; however, when isolated spaces or fine contact holes are formed, the shape of the pattern is markedly deteriorated, and it is difficult to apply the pattern to a device even if a super-resolution technology is employed. Instead, as a method for satisfactorily forming isolated spaces or fine contact holes, negative type chemical amplification pattern forming methods making use of organic developers such as described above are employed.
In more recent years, as one of the measures for the sharp increase in the demand for the miniaturization of contact holes, an attempt to form contact holes that are finer than the conventional contact holes by combining a negative type image forming method using an organic developer with a double exposure technology, is underway at a rapid pace. More specifically, there is known a method of exposing a resist film twice by using a mask having lines and spaces alternately arranged, in which method the mask is disposed such that the line direction of the mask at the time of the first exposure and the line direction of the mask at the second exposure are perpendicular to each other, and a contact hole pattern is formed by developing the resist film after exposure, using an organic developer (see Proceedings of the International Society for Optics and Photonics, Vol. 7274, 72740N (2009) (hereinafter, cited as “Proceedings 7274”); and Proceedings of the International Society for Optical Engineering, Vol. 7640, 764011 (2010) (hereinafter, cited as “Proceedings 7640”)).